Using known files in tests and benchmarks

help
1

I want to run tests and benchmarks against a pre existing datasource. All the data is stored in a directory inside my project folder. What is the best way to use this directory in my tests and benchmarks?

This is what I am currently doing:

let path: PathBuf = env::current_exe().unwrap()
    .parent().unwrap()
    .parent().unwrap()
    .parent().unwrap()
    .parent().unwrap()
    .join("data");

I feel like this is a fragile and ugly solution. Is there a better way of doing this?

2

It sounds like you might want to supply the path as an argument or configuration parameter in some way.

You can also iteratively go up until you find something called data.

3

How can I supply an argument or configuration to tests and benchmarks?

4

You can create a file or use an environment variable.

5

Wouldn't creating a config file have the same problem?

6

Probably yes. An alternative is to use the current directory instead of executable location as base path.

7

Is there no way to get the absolute path to the base of the project at compile time? For example through a macro?

8

If the data is small enough to fit in memory, you can use include_bytes!() to embed it in the benchmark executable. The path will be relative to the source file, so it's usually more reliable.

9

You can check environment variables set by Cargo. Specifically, CARGO_MANIFEST_DIR.

2 Likes
10

For a real-world example of this, have a look at the integration tests for the gcode crate.

I've stored a bunch of example gcode programs under tests/data/ and smoke_test.rs uses
concat!() and env!("CARGO_MANIFEST_DIR") to construct the path passed to include_str!() for embedding the file contents in the test binary.

11

Unfortunately my tests just a large amount of files so it wouldn't be practical to use include_str!() or include_bytes!(), but I will definitely look into the environment variables.

12

Shameless plug: I created a crate called include-dir-macro that lets you include the contents out a large number of files at compile time. It's not perfect, but it should do what you need.

13

@cliff That crate looks interesting. I might actually have I use case for that outside of testing.

1 Like
14

You can figure out fixture's filename using env!("CARGO_MANIFEST_DIR") and some_path_buf.join(), so why not just read the data with std::fs::File like a normal file?

To add to this, another alternative is the include_dir crate. I believe that both use include_bytes!() to embed directory tree's contents into the test binary at compile time though, which may or may not work for your use case.

15

Yes, I have moved to using env!("CARGO_MANIFEST_DIR") instead of env::current_exe() and just reading the files. Thanks for the help!

2 Likes
16

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